Aside from the fact that it is hard to believe a spy - a professional liar (since we simply signed an unspoken pact of trust with him the moment we purchased the book), the author's motivation for spying, and other actions were simply ridiculous and he volunteers to highlight such ridicule by grave contradictions.
First, he says he's chosen to spy for the CIA so that America would save his country from its regime, something some would believe; but when he's offered a salary, instead of rejecting it defiantly and with hurt dignity, he just accepts. Just like that. But to be honest, he did say that money was not his motivation when he was offered the first bonus payment, that's before accepting it on the CIA agent's encouraging words, "Take it, it's yours, you deserve it." Oh, and he didn't it say it out loud, it was an inner dialogue but the clever agent felt his struggle that he couldn't express with a single dignified word (after all, who knows how those agents take such words? She might have apologized, taken back the money, and thanked him for his free work to save his country. But we, the good readers, wouldn't do so, would we? No, we trust an honest spy working for the Iranian government's guards on one side and the CIA on the other, for a pay.)
Now, what about those who though that the idea of seeking help from the US to bring democracy was a stale joke in the first place - those who know its black history of supporting tyrants, imperialism, and unchangeable own interest-driven policies? Like who? Well, like the author himself. At one point he admits that the "foreign policy of the US 'sent mixed signals'" (now that's one good romantic expression.) Yet, while many people made the conclusion that the US will not really scramble to set things right in Iran, our good spy made a different one which nothing could shake, not covert negotiations and support at least.
I can go on like this listing situations where the author blandly shows his disrespect for the reader's intelligence.
There other nice coincidences as well to entertain. The guard who was suspicious about the author dies on their trip to the front right after the author finds out that he started digging. The other guard, the author's boss, whom he finally confronted of his despise for the regime, gets assassinated by an anti government group, while driving his car with the author riding beside him. Luckily, the author, who works for the same establishment, walks out of this unscathed, although the car stopped and the motorcycle-riding assassins could have just walked to him and shot him there. Phew! That was close.
And no, the author didn't wonder for a second about this, so I guess this means we shouldn't either.
An important point to ponder is that the author is a Shiite Muslim as almost all Iranians. Shiites changed a lot in the original Islamic beliefs and are considered non-Muslims by original Muslim scholars (it's hard to have faith in a religion that speaks of a human being trapped in a tunnel for hundreds of years and built on the foundation that he will return.) The author mentions several of such horrific and bloody beliefs (like raping female prisoners before executing them to prevent them from going to heaven) but it should be understood that this is not Islam. While he keeps saying that this is not true Islam, he means only fanaticism, which is wrong in all religions. But at the same time, he attempts to twist some righteous beliefs, like martyrdom, which is respected even aside from religion, for one's country for instance, to show it as brainwash.
All in all, I found the book to be far from believable and more of a CIA propaganda against Iran, although the foundations for Iran's atrocities are there, but it is hard to discern the truth from the lies with the above contradictions and irrationalities so stark.
Note:
For the audiobook, the narration was fine. The narrator used a heavy accent to impersonate the character and seemed to be a Persian speaker as well.